+ Added namespace back
 + Create Namespace instance in test
 + Added test case for Namespace::create
 * Clean up include header files
 + Added Namespace::add_subfile
 + Added unit test for Namespace::remove
 + Added unit test for Namespace::add_subfiles()
 - remove full path from struct Metadata
Merge branch 'master' into uni_namespace
 * Extract get_object_id() to a separate function
 + Added Namespace::getattr()
 + Added test case for Namespace::rmdir()
 + Forward declare leveldb store
Merge pull request #29 from vsfs/uni_namespace

Initial work of the unified namespace.